Bill and Sylvia Shirley on thu 10 dec 98
Hello everybody,
When looking the molecular formulas and percentage alnaysis of many
ceramic materials in the Ceramics Web Materials Database, I found a
percentage given for something called "L.O.I.". Does anybody know what
that stands for? I think it may be the same as "I.L." on the Clay and
Feldspar Analysis Charts in Chappell's book, but I'm not sure.
Thanks.
Sylvia
Gavin Stairs on thu 10 dec 98
At 09:52 AM 12/10/98 EST, you wrote:
>----------------------------Original message----------------------------
>Hello everybody,
>
>When looking the molecular formulas and percentage alnaysis of many
>ceramic materials in the Ceramics Web Materials Database, I found a
>percentage given for something called "L.O.I.". Does anybody know what
>that stands for? I think it may be the same as "I.L." on the Clay and
>Feldspar Analysis Charts in Chappell's book, but I'm not sure.
LOI = Loss On Ignition
IL = Ignition Loss
Both terms mean that mass of the material which became volatile and escaped
the analysis. This is principally water, sulphur and carbon in various
forms, but may also include halides (Cl, Fl, Br, etc.), noble gasses (He,
Ne, Ar, etc), other non-metals (O, N), and to some degree the more volatile
metals, such as lead. Most potter's analyses are intended to show the
metals and metalloid (plus phosphorus) content, reported as oxides of a
particular degree or oxidation (e.g., iron as Fe2O3 or FeO2). Most of the
volatiles are therefore not of interest, and the LOI or IL figure is useful
simply to tell how much extra material must be used in order to obtain the
analysis quantities of the oxides, as in preparing a recipe.
However, any loss of metals is a fault in the analysis, and much of the
skill in analysis comes in the form of sample preparation technique so as
to preserve the metallic content of the sample while ashing and separating
it from the volatiles. In the case of spectroscopic analysis as a flame
spectrum, the quantity of material present is measured by comparing the
brightness of a particuar spectral line, chosen for its particularity to a
single ionic form of the metal in question, and for its intensity relative
to other nearby lines, to that obtained from a sample of known
concentration. The accuracy of the result depends on many things, but
directly on the sample preparation technique.
In the case of an analysis for a volatile metal, like lead, particular care
must be taken to preserve that metal from volatilization, or loss from the
sample during preparations. Ashing is therefore usually done by acid
digestion, and no high temperature steps are used. Acids used in this step
are composed only of volatile elements, so the metal concentration
information can be preserved throughout the preparation.
Gavin
Gavin Stairs
Stairs Small Systems (S3)
921 College St., # 1-A
Toronto, Ontario, Canada M6H 1A1
(416)530-0419 stairs@stairs.on.ca
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